The present invention relates generally to pulleys and pulley constructions and more particularly to methods and apparatus for fabricating pulleys.
Numerous methods have been developed for fabricating pulleys of different sizes and shapes including such diverse methods as casting, stamping, rolling, spinning or combinations thereof. A commonly employed method involves a stamping operation in which a pulley is fabricated from sheet stock by progressive dies. While this operation produces an acceptable pulley construction, substantial amounts of waste material result from both the trimming operation necessary to obtain a circular blank as well as from punching or drilling operations necessary to provide shaft or other mounting provisions in the hub portion thereof. Further, additional material is required as generally one of the V-groove defining walls will be double thickness. Thus, the additional material required must necessarily result in increased costs of producing such pulleys. Such costs are similarly present in those operations which combine stamping and rolling operations. Further, when a rolling operation is included, additional machine set up time is required in order to properly index the roller advancing mechanisms as well as requiring additional labor to properly maintain these mechanisms.
Another method commonly employed in fabricating pulleys involves a slitting operation in which flat stock is blanked into discs which are then provided with a circumferential V-groove by slitting the edge around the circumference and forming these slit portions axially outward to thereby define a V-groove therebetween. While this method avoids the extra material required by the double wall thickness in the stamping operation, it nevertheless still is a relatively expensive construction due to the increased maintenance costs associated with the required cutters.
The present invention, however, provides a pulley construction method and apparatus for executing the method which enables maximum flexibility in design strength for both the rim portion and hub portion thereby allowing fabrication of pulleys having sufficient strength to accomplish their intended function while avoiding the added cost of excessive structural strength in other portions. Further, as the present invention utilizes cylindrically-shaped blanks for fabrication of the pulley rim, all waste is substantially eliminated. Also, the apparatus for forming a pulley by the method of the present invention is less complex and therefore not only less expensive but more easily maintained and less subject to unexpected downtime. Further, production may be easily shifted from one side pulley rim to another by merely exchanging dies on the machine.
Additional advantages and features of the present invention will become apparent from the subsequent description and the appended claims taken in conjunction with the accompanying drawings.